Towards SSH3: how HTTP/3 improves secure shells (2312.08396v1)

Abstract: The SSH protocol was designed in the late nineties to cope with the security problems of the telnetf family of protocols. It brought authentication and confidentiality to remote access protocols and is now widely used. Almost 30 years after the initial design, we revisit SSH in the light of recent protocols including QUIC, TLS 1.3 and HTTP/3. We propose, implement and evaluate SSH3, a protocol that provides an enhanced feature set without compromise compared to SSHv2. SSH3 leverages HTTP-based authorization mechanisms to enable new authentication methods in addition to the classical password-based and private/public key pair authentications. SSH3 users can now configure their remote server to be accessed through the identity provider of their organization or using their Google or Github account. Relying on HTTP/3 and the QUIC protocol, SSH3 offers UDP port forwarding in addition to regular TCP forwarding as well as a faster and secure session establishment. We implement SSH3 over quic-go and evaluate its performance.

• The paper introduces SSH3, a novel secure shell protocol that leverages HTTP/3 and QUIC for lower latency and efficient resource management.
• It utilizes HTTP-based authentication to integrate diverse mechanisms like OpenID Connect and basic methods, broadening secure access with major identity providers.
• SSH3 mitigates TCP limitations by embracing QUIC’s features, resulting in improved resistance to connection resets and faster session initiation.

Analysis of "Towards SSH3: how HTTP/3 improves secure shells"

This paper presents SSH3, a novel approach to modernize the Secure Shell (SSH) protocol by leveraging contemporary network standards such as HTTP/3 and QUIC. Over the course of several decades, SSH has served as a cornerstone for secure remote access. Nonetheless, evolving communication protocols necessitate a reevaluation of SSH's architectural underpinnings. This work critiques traditional SSH implementations and proposes a framework to enhance its efficacy within present-day networking environments.

SSH3 builds atop HTTP/3, which amalgamates the benefits of TLS 1.3 with QUIC's transport traits, offering lower latency and more efficient resource management. In this context, the authors investigate the robustness of SSH3 against connection reset attacks and network scans, an improvement facilitated by QUIC's encryption and seamless connection migration capabilities. This modern stack is conducive to the merger of security and performance, streamlining initial connection establishment while maintaining cryptographic integrity.

Key Features and Performance

The SSH3 implementation harnesses HTTP-based authorization, allowing for an enriched set of authentication mechanisms beyond typical SSH practices—such as basic authentication and OpenID Connect. By utilizing HTTP's extensible authentication framework, SSH3 enables seamless integration of popular identity providers like Google and Microsoft. Furthermore, the proposed architecture facilitates both TCP and UDP port forwarding, extending beyond SSH's historical constraints to support latency-sensitive applications via UDP encapsulation.

The paper highlights considerable reductions in session completion times using SSH3 in comparison to SSHv2. In scenarios tested, SSH3's quick setup significantly diminished connection establishment latency, thanks to the single round-trip initialization afforded by HTTP/3. Empirical benchmarks further demonstrate SSH3's proficiency in an interactive shell environment, achieving lower keystroke latency than SSHv2. Nonetheless, it is important to note that SSH3 currently incurs a throughput trade-off due to the computational demands of its components such as QUIC and Go language runtime.

Implications and Prospective Deployment

SSH3's foundations forgo TCP, relying on QUIC's robust transport characteristics. This paradigm shift enables the protocol to mitigate TCP-specific limitations, such as head-of-line blocking and RST-based denial-of-service attacks. By embedding SSH within HTTP/3's infrastructural fabric, SSH3 potentially transforms secure remote access into a modernized, web-friendly service. Moreover, the adoption of TLS 1.3 natively augments cryptographic strength across SSH3 deployments, capitalizing on the secure session management and innate forward secrecy of TLS.

From a theoretical standpoint, SSH3 underscores the alignment of secure communication protocols with evolving Internet usage patterns. The proposal pragmatically positions the complexity of SSH within the ubiquitous constructs of HTTP, simplifying protocol operations. From a practical perspective, SSH3 instantiates a pathway towards standardizing secure interactive access across diverse network configurations and device ecosystems, thus broadening the operational span of secure shell utilities.

Future Developments

The authors suggest several avenues for further refinement of SSH3. The prompt engagement of the research and open-source communities is pivotal to collaboratively advance the protocol's design and integration within existing systems. Efficiencies in throughput optimization remain a critical focus area for future iterations of SSH3, ensuring it can fulfill high-performance requirements without undermining operational simplicity. With the underlying framework outlined, SSH3 stands to benefit from engagement with network protocol standard bodies to ensure broad acceptance and compatibility with Internet infrastructure.

In summary, this paper positions SSH3 as a forerunner in the effort to reconcile the SSH protocol with contemporary Web architecture, maintaining rigorous security without sacrificing utility and responsiveness. The exploration of HTTP/3-based secure shells heralds an exciting evolutionary trajectory for encrypted interactive sessions in rapidly advancing networking environments.